Protection of well casing for in situ combustion



April 27, 1965 H. w. PARKER 3,180,411

PROTECTION OF WELL CASING FOR IN SITU COMBUSTION Filed May 18, 1962 2Sheets-Sheet 1- FIG. 2

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H. W. PARKER BY y A TTORNEVS FIG.

April 27, 1965 H. w. PARKER PROTECTION OF WELL CASING FOR IN SITUCOMBUSTION Filed- May 18, 1962 2 Sheets-Sheet 2 INVENTOR. H W PARKER ATTORNEKS lhldddll Patented Apr. 2?, 1%55 3,18%,411 RQT-"QTE@N QB WELLQASlNG FUR 1N SITU CGIvlBUS'llGN Harry W. Parker, Eartlesville, @kla,assignor to Phillips Petroleum (Zompany, a corporation oi Delaware FiledMay 18, $62, Ear. No. 195,766 8 Ciaims. (Ql. led-ll) This inventionrelates to a method and apparatus for protecting well casing and tubingfrom overheating during in situ combustion.

Frequently a relatively deep oil structure is being produced byconventional methods (such as pumping) and the casing and tubing leadingto this structure pass thru other oil bearing strata which are amenableto production by in situ combustion. To illustrate, in North and WestCentral Texas, the Ellenberger formation lies about 2280-24-00 feet deepwhile the Strawn sand is about 1600 feet deep and direcdy over theEllenberger stratum. The Ellenberger stratum is being produced by anumber of wells thru casing and tubing extending thru the Strawn sand.It has recently become desirable to produce the Strawn sand by in situcombustion. However, by igniting the Strawn sand around certain wellstherein and in jecting combustion gas to the ignited area, the resultingcombustion zone is moved thru the sand to other wells therein andcontacts the deeper wells extending to the Ellenberger stratum. Sincethe temperature in the burning stratum reaches levels (IOOO-ZQOG" F.)which melt or otherwise damage the casing and tubing of the deeperWells, it is essential to protect these wells by some method. Also, inproducing hot gases from a combustion zone in an oil bearing stratum,the production well tubing and casing are overheated. This invention isconcerned with a method of protecting such wells from damaging ternerature.

Accordingly, it is an object of the invention to provide a process andapparatus for protecting the casing and tubing of a well extending thrua shallow stratum, being produced by in situ combustion, to a deeperproducing formation. Another object of the invention is to protect thecasin and tubing of wells extending to or thru a burning carbonaceousstratum. Other objects of the invention will become apparent to oneskilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises providing a cooling zone orchamber just above the lower end of a casing and tubing in a productionwell adjacent a stratum undergoing in situ combustion, and maintainingsuitable vaporizable liquid coolant such as water, in the lower sectionof said chamber so as to dissipate heat from the casing and tubing. Thechamber may extend all of the way to the well head so that adequatecondensation space is provided in the cool annulus nearer the well head.

Another aspect of the invention comprises providing a cooling zone orchamber around a well casing extending through an upper stratum, beingproduced by in situ combustion, to a lower producing stratum andmaintaining a suitable liquid coolant in the cooling zone whichdissipates the heat of combustion of the carbonaceous material adjacentsaid casing. In one aspect of the invention, the tubing-casing annulusis packed oif below the upper stratum and the annulus above the packeris filled with the liquid coolant to a level at least as high as the topof the adjacent stratum. In another aspect of the invention, a largercasing is extended from ground level through the upper stratum (to beburned) and a smaller diameter casing is set from a level substantiallyabove the upper stratum extendin to the lower producing stratum, therebyproviding an annulus between the lower section of the upper casing andthe upper section of the lower casing which is sealed off, with thecoolant therein,

fter removing the air. This section of the two casings is preferablyfabricated above ground with a coolant sealed therein and the same isthen set at the proper level in the well so that the coolant extendsfrom a level below the upper stratum to a level above same.

A more complete understanding of the invention may be had by referenceto the accompanying schematic drawing of which FIGURE 1 is an elevationin partial section of an arrangement of wells in accordance with theinvention; FIGURE 2 is a fragmentary elevation in cross sectioniHustrating a second embodiment of the invention; PlGURE 3 is anelevation in partial section of a production well arrangement using theinvention; and FIGURE 4 is a fragmentary elevation in partial crosssection showing a second embodiment of the device of FIGURE 3.

Referring to FIGURE 1, an upper stratum 10 is penetrated by wells 12 andl4- and a lower producing stratum 16 is penetrated by well l8. Well 18is provided with casing 29 extending through stratum 1t) and with tubing2.2. A packer 24 is set between tubing 22 and casing 20 just belowstratum 10 and a suitable liquid coolant 26 is positioned in the annularcooling chamber above packer 24 so that the liquid extends at least tothe upper level of stratum 1-9.

Well 12 is provided with casing 28 and tubing 39 extending to a leveladjacent stratum 19. Well 14 is provided with similar casing 32 andtubing 34. A pump 36 is positioned on the lower end of tubing 22 in well18.

In operation, it is conventional to ignite stratum 19 around well 12 byany suitable means, such as burning a charcoal pack in well 12 Withinstratum l0, and injecting a combustion supporting gas, preferably,containing a small concentration of fuel gas (1-3 or 4% by volume)through well 14 (as through tubing 34) so as to force the combustionsupporting gas throughthe stratum to the ignited area around well 12 andcause the combustion zone to move through stratum ill to well 14. Inpassing well 18, the combustion zone heats casing 26 and the coolant 26in the annular cooling zone adjacent stratum 19 is heated and boiled sothat the heat of vaporization dissipates the heat imparted to the casingby the combustion and keeps the casing below a deleterious temperature.The vaporized coolant is cooled on the side of casing 20 above stratumit which results in condensation and refluxing.

Liquids which function as desirable coolants include mercury, sulfur,stable organic compounds such as polyphenyls, water, kerosene, highboiling point alcohols such as ethylene glycol, etc. Polyphenyls arepreferred because they are cheap and stable at temperatures up to 800 to900 F. Any coolants known to the art may be utilized in the coolingzone. The invention is not dependent upon the use of any particularcoolant.

Referring to FIGURE 2, a prefabricated section of easing ll comprises alarge diameter casing 42 extending to a level below stratum it) and asmaller casing 44 of smaller diameter, extending to a levelsubstantially above stratum 1b to provide ample condensing space 4-6above liquid coolant '43 in the resulting annulus between the twocasings. Cooling chamber 59 is sealed gas tight by annular plate 52welded onto the bottom of casing 42 and onto casing 44, and by plate 54welded onto the top of easing d4- and to casing 42. It is to beunderstood that casing 42 extends to the Well head and casing 44 extendsto the proximity of the lower producing zone.

When casing section as is fabricated above ground, coolant 48 ispositioned therein and the condensation space as is preferably evacuatedbefore sealing the cooling chamber. This facilitates the cooling processin which coolant 43 is boiled and condensed in the upper section 45 ofthe cooling chamber. When utilizing organic compounds as coolingliquids, it is desirable to fill ers may be set in lieu of annularplates 52 and 54 to seal oil the cooling chamber. Before setting theupper packer, the coolant is positioned in the cooling chamber 50.

Referring to FIGURE 3, a stratum 60 is penetrated by a well 62 providedwith casing 64 and tubing 66 extend- ,ing to a-level adjacent stratum60. An annular combustion zone 68 surrounds Well 62 and hot combustiongases are being driven into the well below the tubing. A packer 70 sealsoff the tubing-casing annulus adjacent'the lower end of the tubing,providing a cooling chamber 72, extending to the well head. Liquidcoolant 74 fills the lower section of chamber 72 to level 76. Thesection of chamber 72 above level 76, designated 78, comprises acondensation Zone or section.

:Boiling liquid dissipates heat from the gases passing thru the'tubingto the well head by indirect heat exchange 3. The structure of claimlrwherein said chamber is formed bya first larger diameter casing insaid well extending to a level just below the bottom of said secondstratum; a second casing of smaller diameter extending firoma levelsubstantially above said second stratum to a level substantially belowsaid first casing; and closure means in the resulting annulus betweenthe overlapping casings at levels above and'below said second stratumseated against the casings and sealing said chamber, said coolantoccupying only about the lower half of said chamber but at least to thetop ofsaid second stratum.

4. The structure of claim 3 wherein said chamber is at 'least partiallyevacuated. I

therewith thru tubing 66 to prevent damage to the tubing and easing. V

In FIGURE 4, production well 80 penetrates oil stratum 82 undergoingproduction by in situ combustion. Well 80 is provided with casing 84 andtubing 86, terminating just above the stratum. Cooling chamber 88 isformed by a cylindrical section of conduit 90 sealed to the lower end oftubing 86 by annular plate 92 and by packer 94 at its upper end.Asbestos 'or refractory concrete packing 96 packs off the lower end ofannulus 98 to prevent condensation of oil in this annulus.

Positioning packer 9.4 in the mannershown in FIG- URE 4 allows use of apacker with non-metallic seals.

The remoteness from the hot gases entering the Well below plate 92 andthe presence of coolant adjacent the .packer protects the packer fromexcessive heat and eliminates the problem of positioning seats in thecasing and the tubing required for metal seals.

Certain modifications of the invention will become ap parent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

I claim: I

1. In an earth structure wherein a first oil-bearing stratum liessubstantially below a second oil-bearing stratum and is penetrated by awell including casing and .tubing passing thru said second stratum, andsaid second stratum is being produced by in situ combustion so that .a'combustion zone at a temperature in the range of 1000 to 2000 F. ismoved thru said second stratum adjacent said casing and tubing, saidsecondstratum being at said temperature: a structure for protecting saidcastically from just below the bottom of said second stratum 5. Thestructure of claim 3 wherein hydrogen occupies space in said chamberabove said coolant and said coolant comprises an organic compound.

6. In an earth structure wherein an oil-bearing stratum is beingproduced by in situ combustion comprising igniting said stratum andinjecting O -containing gas into the ignited area from an injection'well and producing hot hydrocarbons and combustion gases thru aproduction well therein thru tubing and easing extending to a leveladjacent said stratum, whereby said hot gases heat said stratum adjacentsaid casing to a temperature in the range of 1000 to.2000 F. andoverheat and damage said casing and tubing; a' structure comprisingclosure means sealing 05 the tubing-casing annulus at said level formingan elongated upright annular chamber, said closure means comprising acylindrical section smaller in diame .ter than said casing extendingupwardly from the lower end of saidtubing. and sealed therewith at itslower end .and a sealing means between said casing and said sectionadjacent its. upper end, whereby last said sealing means issubstantially above the bottom of said chamber; and a vaporizable liquidcoolant in a lower section of said chamber providing a verticallyelongated condensation section in the upper section of said chamber.

7. The structure of claim 6 including packing means inthe annulusbetween said casing and said section at its lower end 'to exclude oilvapors from last said annulus.

, 8. A process for producing oil from a second oil-bearing stratumoverlying a deeper first oil-bearing stratum to'which a first wellhaving a casing and tubing string extends, Said first well passing thru,said second stratum, which comprises igniting said second stratum arounda second well therein; feeding air to the ignited area thru at least onewell in said second stratum so as to move a combustion zone therethru ata temperature in the range ,Of 1000 to 2000 F. adjacent said first well,and recover- ;maintaining a'liquid coolant in the annulus of said firstto substantially above the top thereof, said casing forming a theoutermost wall'of said chamber; and a vaporizable liquid coolant insaidchamber extending from the bottom thereof only to a level just above thetop of said secondmstratum thereby forming a vertically extended vaporzone in said chamber above'said liquid.

' 2. The structure of claim 1 wherein saidchamber is formed by settingapacker' around said tubing adjacent the bottom of said second stratumto seal off the casingtubing annulus. a

Well extending from just below to just above said second stratum, andproviding a vertically extended vaporizing zone for .saidvcoolant insaidannulus above saidcoolant for cooling and refluxingsaid coolant.

References Cited bythe Examiner UNITED STATES PATENTS 1,413,197' 4/22Swan 16657 2,346,060 4/44 Yeatman 166-89 2,530,280 11/50 'Ackley l66-3912,649,915 8/53 Miller 166-224 3,013,609 12/61 Brink -Q. 166-39 BENJAMIN'HERSH, Priniary Examiner.

8. A PROCESS FOR PRODUCING OIL FROM A SECOND OIL-BEARING STRATUMOVERLYING A DEEPER FIRST OIL-BEARING STRATUM TO WHICH A FIRST WELLHAVING A CASING AND TUBING STRING EXTENDS, SAID FIRST WELL PASSING THRUSAID SECOND STRATUM, WHICH COMPRISES IGNITING SAID SECOND STRATUM AROUNDA SECOND WELL THEREIN; FEEDING AIR TO THE IGNITED AREA THRU AT LEAST ONEWELL IN SAID SECOND STRATUM SO AS TO MOVE A COMBUSTION ZONE THERETHRU ATA TEMPERATURE IN THE RANGE OF 1000 TO 2000* F. ADJACENT SAID FIRST WELL,AND RECOVERING PRODUCED HYDROCARBONS FROM A WELL IN SAID SECOND STRATUM,THEREBY NORMALLY EXPOSING THE CASING OF SAID FIRST WELL TO SAIDTEMPERATURE; PRIOR TO MOVING SAID COMBUSTION